Process for producing a net



May 30, 1967 v. s. VAN SCOY PROCESS FOR PRODUCING A NET Filed Feb. 4,1964 INVENTOR VICTOR SAMUEL VAN SCOY ATTORNEY United States Patent3,322,021 PROCESS FOR PRODUCING A NET Victor Samuel Van Scoy, Newark,Del., assignor to E. I. du Pont de Nemours and Company, Wilmington,Del., a corporation of Delaware Filed Feb. 4, 1964, Ser. No. 342,377 1Claim. (Cl. 871) This invention relates to improvements in nets and,more particularly, to fish nets or safety nets. The inventionspecifically relates to the encapsulating of knots used in such nets anda method of manufacturing such encapsulated knots.

The problem of knot slippage is one that has been recognized bymanufacturers of netting for many years and as a result various methodshave been suggested for overcoming this problem. Such methods includethe modification of the elastic memory of the twine material by wetheat-setting and drying of the knot while under tension as described inUS. Patent 2,653,372. While this method has improved the knot retention,it does not permanently secure the knot or provide protection frominternal abrasion during use.

Several processes have also been suggested for applying heavy coatingsof resinous materials to an entire net to fix the knots and protect thefilamentous twines from the deg'radative action of sun, water, sand, orother elements of exposure. Such coatings have not been fully successfulbecause of the increase in weight, change in hand, or still otheradverse elfects. Another approach at overcoming the problem has involvedimpregnation of the cord or twine of the netting with a solution of aresin in order to stiffen the yarn within the knot. This method also,however, results in an undesirable stiffening of the twine segmentsbetween knots. Accordingly a compromise must be sought between usingsuflicient stiffening agent to hold the knots but not so much that thestiffness of the net is unduly increased. Such procedures and productsare described in US. Patent 2,823,576 and in U.S. Patent 2,823,575.Impregnation of the twine or cord prior to fabrication of the net hasalso been described in US. Patent 2,590,586.

As a further problem in the fabrication of fish nets, it has also beenrecognized that knot strength is normally less than the strength of thestraight seine twine. Means heretofore suggested for improving knotslippage have not generally been satisfactory for also avoiding the knotstrength problem.

This invention has as an object an encapsulated knot structure whicheliminates knot slippage, increases knot strength, and providesprotection against the degradative action of sand, water, and otherelements of exposure.

A further object is to increase knot strength and, consequently,over-all net strength or, conversely, to permit a decrease in net weightfor a given net strength requirement by the use of finer twines.

A still further object is to provide a method of manufacturing nets ofincreased strength.

Other objects will be apparent from the remainder of the specificationand claims.

In accordance with the invention a method is provided for producing afish net of improved resistance to knot slippage. The method comprisesforming a fish net of filamentous twine, applying solely to the knot andimmediately adjacent twine portions of the net a waterproof adhesiveresin to encapsulate each of the knots, and solidifying the adhesiveresin. It is important that the segments of twine between knots beuncoated and essentially free of said adhesive resin. It will beunderstood that in encapsulating a knot, the adhesive resin shouldpenetrate and at least partially fill the void between the twines form-3,322,021 Patented May 30, 1967 ing the knot. Although the knot may havefirst been pulled tight to a set condition, it is highly preferred toapply the encapsulating adhesive material after the knot has been formedbut not tightened. The encapsulating material may be a solution of aresin in a solvent, such as a 15% solution of a polyamide resin inalcohol and water, or polyvinyl acetate in water, or a hot-melt adhesivehaving good adhesive characteristics for the fiber used in manufacturingthe net.

The knot encapsulating process can be conveniently carried out on aconventional netting machine which has been modified to include acontainer for an adhesive resin solution or melt and means forintermittently immersing or coating a row of knots with the adhesiveresin.

This invention will be further described with reference to theaccompanying drawings wherein:

FIGURE 1 is a diagrammatic representation of a portion of a fish netprepared according to the invention.

FIGURE 2 is a diagrammatic illustration on an enlarged scale of anencapsulated knot of the net of FIG- URE 1.

FIGURE 3 is a diagrammatic side view of a netting machine equipped withmeans for applying adhesive to the knots of the net.

FIGURE 4 is also a side view of a netting machine equipped withalternate means for applying adhesive to the knots of the net.

Referring more particularly to the drawings, FIGURE 1 iilustrates asection of atypical net treated in accordance with the invention showingthe knots 11 produced at the cross-over point of the twines -10 of thenet, each knot being encapsulated by a globule of adhesive resin 12.FIGURE 2 shows the adhesive 12 as completely surrounding the loops ofthe knot 11 and extending a short portion along the twines 10. It willbe seen that the adhesive has been confined almost exclusively to theknot portions of the net.

The operation of applying the adhesive to the knot can best beunderstood by referring to FIGURE 3, in which 13 represents generally aconventional netting machine which forms the knots 11 in a customarymanner. .Feed rolls 14 transmit the loosely knotted net structurethrough the machine and into close proximity with a tank or trough 15filled with a solution, melt or dispersion of adhesive 16. If theadhesive is of the melt-type, the molten condition is maintained bysuitable heating devices, not shown. The netting advances and firstpasses about a nose bar 17 which extends across the width of the net andwhich is mounted in a stationary position to the frame of machine 13.The net then discharges from the machine through take-up rolls 18, thesebeing adequately spaced from trough 15 to allow the adhesive applied atnose bar 17 to solidify, e.g. by cooling or by loss of solvent. Theadhesive 16 is applied to the row of knots aligned on the rounded pointof the nose bar 17 while the net is stationary during the formation of anew row of knots on the netting machine. While a row of knots is inposition on the blunt edge of the nose bar, the adhesive trough 15 israised by a suitable mechanical connection activated by an indexingdevice attached to the feed roll 14.

A preferred apparatus for use with lighter-Weight netting is illustratedby FIGURE 4 In this embodiment the netting machine 13 is adjusted tomanufacture a loosely knotted net which is forwarded from the machine inclose proximity to a rotating roll 40 which dips in a trough of adhesive41. As the knotted net structure pauses in its advance past the rotatingroll 40, a movable bar 42 presses against the net to move a row of knots43 into contact with the adhesive coating on rotating roll 40. Theamount of adhesive applied to the individual knots in this way may bevaried by suitable adjustment of the timing of the movement of bar 42through use of an indexing mechanism connected to the feed roll 14. Thespeed of rotation of the roll 40 and other factors such as the depth ofpenetration of the roll into the adhesive trough 41, the viscosity ofthe adhesive in the trough, or the use of grooves n the face of theroll, are also effective in controlling the amount of adhesive appliedto the individual knots.

It is to be understood that the present invention is not limited to theparticular type of twineemployed. Also the adhesive may be anyfilm-forming resin, either thermoplastic or thermosetting, which iswater-insoluble and forms a good bond on the twine. Thus, the adhesivemay be a polyester resin, a polyvinyl resin, a polyamide resin, apolystyrene resin, a polyacrylic resin, or copolymers of any of theabove resins of the same type, or different types. 7

By applying the adhesive to a loosely tied knot, complete penetration ofthe adhesive around the twine inside the knot permits the adhesive, whenit has been dried or otherwise solidified or hardened, to form a saddleor cushion which reduces the fiber-to-fiber cutting and therebyincreases knot strength over and above the increase obtained in coatingtightened knots. The hardened adhesive material also serves to transmitsome of the tensile load applied to the twine around the knot ratherthan through the knot. In actual use, the hardened adhesive alsoprevents sand or grit from entering the knot so that the abrasive actionof these materials upon the twine within the knot is diminished.

It is a significant feature of the invention that nets so produced havesuffered no losses in flexibility. Also the increase in weight of theknot due to the addition of the encapsulating adhesive is generallyabout 5 to of the weight of the knot, analrnost insignificant portion ofthe total weight of the net. 7

The following examples will further illustrate the practice of theinvention. Unless otherwise indicated, parts and percentages are byweight.

EXAMPLE I V p A test net was prepared on a conventional netting machineusing twines of 840 denier nylon 66 seine twine; The adhesive employedwas a 15% solution in an 80%" ethanol/ 20% water mixture of a polyamideformed by the copolymerization of hexamethylene diammonium adipate,hexamethylene diammonium sebacate, and caprolactam. One section ofnetting was treated while the knots were loose 'and another section wastreated while the minute in order to measure the breaking strength. Thefollowing data show the surprising advantage of encapsulating knots bythe technique of the invention. a

Mesh breaking Nylon net: strength, in pounds Untreated 33.70 Knots tightwhen encapsulated 44.50 Knots loose when encapsulated 47.00,

These results show that the tight encapsulated knot has an increase of32% of the strength of the untreated knot and the loose encapsulatedknot has a 38% increase in breaking strength over the untreated knot.

EXAMPLE 11 Samples of gill nets made from 210 denier, nylon 66 seinetwine were prepared and encapsulated using the encapsulating process andadhesive resin of Example 1.,

Immersion tests were performed upon these and control samples todetermine the rate at which a loss in strength occurs under conditionsof continuous exposure while submerged in a fresh water lake. After oneyear exposure,

the untreated control net had lost over 10% of its original Method forproducing a net of improved resistance to knot slippage and breakagecomprising forming a fish net of filamentous twine in which knots areformed but not tightened, applying solely to the untightened knot, the

twinerwhich forms the knot and immediately adjacent twine portions ofthe net a waterproof adhesive'resin to encapsulate each of the knots andthe twine which forms the knot, thereafter tightening the knots beforethe resin solidifies and finally solidifying the adhesive resin.

References Cited UNITED STATES PATENTS 2,590,586 3/1952 Thompson et a18712 X 2,653,372 9/1953 Johnson et al 8712 X 2,823,575 2/1958 Needham etal. .'87'--12 X 2,823,576 2/1958 Needham et al. 8712 X 2,868,676 1/ 1959Ljungbo 87-1 X 2,870,669 1/1959 Kopacki 8712 X 2,945,412 7/1960 Johnson8712 X FOREIGN PATENTS '7 685,623 1/ 1953 Great Britain.

FRANK I. COHEN, Primary Examiner. I. PETRAKES, Assistant Examiner.

